gold membership redeemed under wrong gamertag. HELP!

You would need to contact support to see if they can cancel the subscription and give you a token for the remaining time to redeem on the correct account. 1-800-4my-xbox if you're in the US/Canada or
support.xbox.com/contact-us

Hi there,

The code can be kept for later redemption, however you can redeem it now and it will stack on top of your current membership, giving you 24 months added to your gamertag.

I'm not sure what you mean by your second point, pre-paid subscription cards can only be redeemed for Gold membership activation on your gamertag.

Hope that helps.

I'm guessing he may have redeemed on the wrong gamertag. It doesn't just disappear, if he were hacked he wouldn't be able to sign in, or he would and it would still be gold because they use it on the gamertag, they can't just take your subscription. If
his account was suspended or banned he wouldn't be able to even access Silver membership. I would try redownloading the profile, signing into ALL the profiles on the console and checking their memberships. Just a side note in case you were un-aware Gold subscriptions
are profile based not console based. So if it's redeemed on one another on the console is not going to be gold.

i tried to redeem a 3month xbox live gold membership code and it said the same thing to me something went wrong. Ive been trying all day! Help Please!

Just so you know for the future, your gold membership isn't tied to the console it's tied to the Microsoft Account (gamertag) you make and redeem or purchase the membership on.